1. Field of the Invention
The present invention relates to a control apparatus which detects voltages at a plurality of positions on an integrated circuit and controls a supply voltage to be supplied to the integrated circuit, based on the detected voltages. Also, the invention relates to a semiconductor integrated circuit apparatus which comprises such control apparatus. Further, the invention relates to a source voltage supply control system which supplies a voltage to such semiconductor integrated circuit apparatus.
2. Description of the Related Art
Many of the recent semiconductor integrated circuit apparatuses are large in size and have complex functionality. In addition, there are strong demands for high integration, high speed, and low voltage of an integrated circuit, and thus, problems regarding source wirings and signal wirings are becoming serious. As for source wirings, voltage drop (IR-drop) that is caused by a resistance component of a source wiring itself and upon operation of an integrated circuit affects the operating speed of the integrated circuit, and therefore, a malfunction may possibly occur. In addition, by metal atoms moving in a wiring due to transient current, electromigration that may break the wiring or may cause a short circuit with other conductors may possibly occur. The lower the voltage, the higher the ratio of the amount of voltage drop; therefore, voltage drop is one of the serious problems in the recent semiconductor integrated circuit apparatuses.
In view of this, a semiconductor integrated apparatus is proposed (see, for example, Japanese Patent Application Laid-Open No. 2001-332699) in which a voltage detection cell is disposed in an appropriate position on a source wiring of a semiconductor integrated circuit, a voltage at that position is detected, and further, voltage drop of the detected voltage is detected, whereby voltage drop on the semiconductor integrated circuit is simply and easily checked and the voltage drop can be compensated.
There is a known technique in which in order to realize low power consumption, a supply of a supply voltage to a circuit block that is not necessary in a certain operation mode is intentionally cut off If such a technique is applied to the aforementioned technique disclosed in Japanese Patent Application Laid-Open No. 2001-332699, in spite of no voltage drop, since a voltage at one of a plurality of circuit blocks becomes 0 V, a determination that there is voltage drop is made and accordingly a high supply voltage is supplied. As a result, the supply voltages to other circuit blocks are increased, causing a problem of a malfunction. Needless to say, even if a supply of a supply voltage is not intentionally cut off, if a supply voltage to an unnecessary circuit block is reduced, the same problem occurs.